1. Field of the Invention
The present invention relates to a positioning or navigation system of a vehicle, and more particularly to a geographic information display apparatus having a function of retrieving geographic information such as, place name, facility name and route name.
2. Prior Art
A GPS (i.e. global positioning system), which is a positioning or navigation system designed to use a plurality of satellites to provide a user anywhere on earth with extremely accurate measurements of its three-dimensional position, has been recently popularized. And, therefore, the development of systems calculating the current position of a mobile object based on such GPS technologies is remarkably progressing.
A CD-ROM (i.e. compact disc ROM) is a recording medium preferably used for such positioning or navigation systems. Electronic maps stored in this CD-ROM have a standardized format, in conformity with which a variety of CD-ROM software are already placed on the market. Thus, development of a system for effectively reproducing or displaying such information of CD-ROM software, i.e. an advanced geographic information display system, is now earnestly expected.
A conventional geographic information display apparatus has a function of registering place names, route names or facility names by pointing a mark spot on the displayed map, so that a designated mark spot and its name memorized in a memory are paired with each other in a "mark spot list". Thus, when a user requests display of a previously marked map, the mark spot list is first displayed on the screen, and then the user is allowed to select a desired one item among registered names on the list. After that, the system automatically displays a map corresponding to thus selected item.
However, this conventional registering function is characterized by unconditional registering which automatically memorizes a name closest to the mark spot regardless of the user's intention. More specifically, according to such a conventional geographic information display apparatus, the names registered are not always adequate for retrieval because the name memorized by a marking operation is the name closest to the marking spot which may not reflect the user's intention. Accordingly, the registered name is possibly different from the name the user intends to register. For example, if a route name such as "Route 66" is located very close to the mark spot, this name will be automatically registered but may not be preferable for the name to be registered because a road such as "Route 66" generally extends long distances and therefore is inconvenient for the user to designate as a spot name.